package com.eistert.java.datastructure._04_LinkedList;

/**
 * @Description: Implement LinkedList with Queue
 * @Author: ai
 * @create: 2023-04-04 18:56
 */
public class _04_LinkedListQueue<E> implements _04_Queue<E> {


    private class Node {
        public E e;
        public Node next;

        public Node(E e, Node next) {
            this.e = e;
            this.next = next;
        }

        public Node(E e) {
            this(e, null);
        }

        public Node() {
            this(null, null);
        }

        @Override
        public String toString() {
            return e.toString();
        }
    }

    private Node head, tail;
    private int size;


    public _04_LinkedListQueue() {
        head = null;
        tail = null;
        size = 0;
    }

    @Override
    public int getSize() {
        return 0;
    }

    @Override
    public boolean isEmpty() {
        return false;
    }

    @Override
    public void enqueue(E e) {
        if (tail == null) {
            tail = new Node(e);
            head = tail;
        } else {
            tail.next = new Node(e);
            tail = tail.next;
        }
        size++;
    }

    @Override
    public E dequeue() {
        if (isEmpty()) {
            throw new IllegalArgumentException("Cannot dequeue from an empty queue.");
        }

        Node retNode = head;
        head = head.next;
        retNode.next = null;

        if (head == null) {
            tail = null;
        }

        size--;

        return retNode.e;
    }

    @Override
    public E getFront() {
        if (isEmpty()) {
            throw new IllegalArgumentException("Queue is empty.");
        }

        return head.e;
    }


    @Override
    public String toString() {
        StringBuilder res = new StringBuilder();
        res.append("Queue: front ");

        Node cur = head;
        while (cur != null) {
            res.append(cur + "->");
            cur = cur.next;
        }
        res.append("NULL tail");
        return res.toString();
    }


    public static void main(String[] args) {

        _04_LinkedListQueue<Integer> queue = new _04_LinkedListQueue<>();
        for (int i = 0; i < 10; i++) {
            queue.enqueue(i);
            System.out.println(queue);

            if (i % 3 == 2) {
                queue.dequeue();
                System.out.println(queue);
            }
        }
    }
}
